1. Field of the Invention
The present invention relates to printing methods, test patterns, methods for producing test patterns, and printing apparatuses.
2. Description of the Related Art
Inkjet printers for printing by ejecting ink are known as an example of printing apparatuses for printing images on various types of media, such as paper, cloth, and film. In such inkjet printers, printing is carried out by alternately repeating the processes of ejecting ink from nozzles and moving the medium in the carrying direction.
FIG. 45A is an explanatory diagram of printing using such an inkjet printer. A head 41 having a plurality of nozzles is moved in a scanning direction and ink is ejected from the nozzles, forming on the paper a band-shaped print image fragment BP1 having the width of the head. Next, a carry unit carries the paper in the carrying direction by a carry amount that corresponds to the width of the head 41. The printer then repeats the same ejection operation and carrying operation to form on the paper a print image in which the print image fragments BP2, BP3, . . . are joined in the carrying direction.
The carry unit for performing the carrying operation carries paper using structural elements such as motors and gears, and therefore, there are instances in which the carry amount comes to include error.
FIG. 45B is an explanatory diagram of printing in a case where there is carry error. When the carry unit carries the paper by a larger carry amount than the carry amount defined as the target (target carry amount) due to carry error, a gap occurs between print image fragments, resulting in a light-colored striped pattern (also referred to as “bright banding,” “white banding,” and “light banding”) like at the border between the print image fragment BP1 and the print image fragment BP2. On the other hand, when the carry unit carries the paper by a smaller carry amount than the target carry amount, overlap between print image fragments occurs due to the carry error, resulting in a dark-colored striped pattern (also referred to as “dark banding,” “black banding,” and “thick banding”) like at the border between the print image fragment BP2 and the print image fragment BP3. The occurrence of such banding leads to a drop in the image quality.
Accordingly, the target carry amount is corrected during the carrying operation in order to limit the impact of such carry errors (for example, see JP 2001-71475A).
(1) To determine a correction amount for the target carry amount, a pattern for testing (test pattern) is printed as a means for detecting the amount of carry error. A plurality of correction patterns in which a correction amount for the target carry amount is changed in a stepwise manner are printed in the test pattern. Then, by selecting the most suitable pattern from among the plurality of correction patterns, the carry error is detected and a correction amount that allows suitable correction to be executed is determined.
Each correction pattern formed in the test pattern corresponds to a specific correction amount. Thus, it is preferable that as many correction patterns as possible are formed in a narrow region on the paper.
(2) Each of the correction patterns in the test pattern have a reference pattern serving as a reference and a comparative pattern formed adjacent in the carrying direction to the reference pattern. Carrying by the carry unit is performed between formation of the reference pattern and formation of the comparative pattern, and by changing this carry amount for each correction pattern, the spacing between the reference pattern and the comparative pattern of each correction pattern is altered, resulting in a correction amount that differs for each correction pattern. An appropriate correction amount is then chosen by selecting the pattern with the most suitable spacing between the reference pattern and the comparative pattern.
As discussed above, a plurality of correction patterns are formed by altering the carry amount of the carry that is performed between formation of the reference pattern and formation of the comparative pattern for each correction pattern, thus changing the spacing between the reference pattern and the comparative pattern in a stepwise manner. Therefore, if the carrying by the carry unit is not accurate, then the spacing between the reference pattern and the carrying pattern of each correction pattern will become unsuitable. However, as discussed above, when the carry amount of the carry that is performed between formation of the reference pattern and formation of the comparative pattern is different for each correction pattern, it is difficult to make the carry unit perform carrying accurately.